copy_status_flags_v4.patch

diff --git a/src/backend/access/heap/vacuumlazy.c b/src/backend/access/heap/vacuumlazy.c
index 4ee1f14854..a00947ea1c 100644
--- a/src/backend/access/heap/vacuumlazy.c
+++ b/src/backend/access/heap/vacuumlazy.c
@@ -4159,6 +4159,12 @@ parallel_vacuum_main(dsm_segment *seg, shm_toc *toc)
 	LVRelState	vacrel;
 	ErrorContextCallback errcallback;
 
+	/*
+	 * A parallel vacuum worker must have only PROC_IN_VACUUM flag since we
+	 * don't support parallel vacuum for autovacuum as of now.
+	 */
+	Assert(MyProc->statusFlags == PROC_IN_VACUUM);
+
 	lvshared = (LVShared *) shm_toc_lookup(toc, PARALLEL_VACUUM_KEY_SHARED,
 										   false);
 	elevel = lvshared->elevel;
diff --git a/src/backend/access/nbtree/nbtsort.c b/src/backend/access/nbtree/nbtsort.c
index 54c8eb1289..af562fcfae 100644
--- a/src/backend/access/nbtree/nbtsort.c
+++ b/src/backend/access/nbtree/nbtsort.c
@@ -1808,6 +1808,13 @@ _bt_parallel_build_main(dsm_segment *seg, shm_toc *toc)
 		ResetUsage();
 #endif							/* BTREE_BUILD_STATS */
 
+	/*
+	 * A possible status flag that can be set to the parallel worker is
+	 * only PROC_IN_SAFE_IC.
+	 */
+	Assert((MyProc->statusFlags == 0) ||
+		   (MyProc->statusFlags == PROC_IN_SAFE_IC));
+
 	/* Set debug_query_string for individual workers first */
 	sharedquery = shm_toc_lookup(toc, PARALLEL_KEY_QUERY_TEXT, true);
 	debug_query_string = sharedquery;
diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c
index 892f0f6799..0fabe95a09 100644
--- a/src/backend/storage/ipc/procarray.c
+++ b/src/backend/storage/ipc/procarray.c
@@ -2638,6 +2638,9 @@ ProcArrayInstallImportedXmin(TransactionId xmin,
  * PGPROC of the transaction from which we imported the snapshot, rather than
  * an XID.
  *
+ * Note that this function also copies statusFlags from the source `proc` in
+ * order to avoid the case where MyProc has xmin but not sets statusFlags.
+ *
  * Returns true if successful, false if source xact is no longer running.
  */
 bool
@@ -2649,8 +2652,8 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc)
 	Assert(TransactionIdIsNormal(xmin));
 	Assert(proc != NULL);
 
-	/* Get lock so source xact can't end while we're doing this */
-	LWLockAcquire(ProcArrayLock, LW_SHARED);
+	/* Get an exclusive lock so we can copy statusFlags from source proc */
+	LWLockAcquire(ProcArrayLock, LW_EXCLUSIVE);
 
 	/*
 	 * Be certain that the referenced PGPROC has an advertised xmin which is
@@ -2663,7 +2666,17 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc)
 		TransactionIdIsNormal(xid) &&
 		TransactionIdPrecedesOrEquals(xid, xmin))
 	{
+		/* Install xmin */
 		MyProc->xmin = TransactionXmin = xmin;
+
+		/*
+		 * Also, copy statusFlags. Flags being copied must be valid copy-able
+		 * flags.
+		 */
+		Assert((proc->statusFlags & (~PROC_COPYABLE_FLAGS)) == 0);
+		MyProc->statusFlags = proc->statusFlags;
+		ProcGlobal->statusFlags[MyProc->pgxactoff] = MyProc->statusFlags;
+
 		result = true;
 	}
 
diff --git a/src/include/storage/proc.h b/src/include/storage/proc.h
index be67d8a861..cfabfdbedf 100644
--- a/src/include/storage/proc.h
+++ b/src/include/storage/proc.h
@@ -65,6 +65,13 @@ struct XidCache
 #define		PROC_VACUUM_STATE_MASK \
 	(PROC_IN_VACUUM | PROC_IN_SAFE_IC | PROC_VACUUM_FOR_WRAPAROUND)
 
+/*
+ * Flags that are valid to copy from another proc, the parallel leader
+ * process in practice.  Currently, flags that are set during parallel
+ * vacuum and parallel index creation are allowed.
+ */
+#define		PROC_COPYABLE_FLAGS (PROC_IN_VACUUM | PROC_IN_SAFE_IC)
+
 /*
  * We allow a small number of "weak" relation locks (AccessShareLock,
  * RowShareLock, RowExclusiveLock) to be recorded in the PGPROC structure